NAME

       v.lidar.correction   -  Correction  of the v.lidar.growing output. It is the last of the three algorithms
       for LIDAR filtering.

KEYWORDS

       vector, LIDAR

SYNOPSIS

       v.lidar.correction
       v.lidar.correction help
       v.lidar.correction [-e] input=name output=name terrain=name  [sce=float]   [scn=float]   [lambda_c=float]
       [tch=float]   [tcl=float]   [--overwrite]  [--verbose]  [--quiet]

   Flags:
       -e
           Estimate point density and distance
           Estimate point density and distance for the input vector points within the current region extends and
           quit

       --overwrite
           Allow output files to overwrite existing files

       --verbose
           Verbose module output

       --quiet
           Quiet module output

   Parameters:
       input=name
           Input observation vector map name (v.lidar.growing output)

       output=name
           Output classified vector map name

       terrain=name
           Only 'terrain' points output vector map

       sce=float
           Interpolation spline step value in east direction
           Default: 25

       scn=float
           Interpolation spline step value in north direction
           Default: 25

       lambda_c=float
           Regularization weight in reclassification evaluation
           Default: 1

       tch=float
           High threshold for object to terrain reclassification
           Default: 2

       tcl=float
           Low threshold for terrain to object reclassification
           Default: 1

DESCRIPTION

       v.lidar.correction is the last of three steps to filter LiDAR data. The  filter  aims  to  recognize  and
       extract attached and detached object (such as buildings, bridges, power lines,  trees, etc.)  in order to
       create a Digital Terrain Model.
       The  module, which could be iterated several times, makes a comparison between the LiDAR observations and
       a bilinear spline interpolation with a Tychonov regularization parameter performed on the TERRAIN  SINGLE
       PULSE  points only. The gradient is minimized by the regularization parameter.  Analysis of the residuals
       between the observations and the interpolated values results in four cases (the  next  classification  is
       referred to that of the v.lidar.growing output vector):
       a) Points classified as TERRAIN differing more than a threshold value are interpreted and reclassified as
       OBJECT, for both single and double pulse points.
       b)  Points  classified  as  OBJECT  and  closed  enough  to  the interpolated surface are interpreted and
       reclassified as TERRAIN, for both single and double pulse points.

NOTES

       The input should be the output of v.lidar.growing module or the output of this v.lidar.correction itself.
       That means, this module could be applied more times (although, two  are  usually  enough)  for  a  better
       filter  solution.  The  outputs  are  a vector map with a final point classification as as TERRAIN SINGLE
       PULSE, TERRAIN DOUBLE PULSE, OBJECT SINGLE PULSE or OBJECT DOUBLE PULSE; and an vector map with only  the
       points  classified  as  TERRAIN  SINGLE  PULSE  or  TERRAIN  DOUBLE PULSE.  The final result of the whole
       procedure (v.lidar.edgedetection, v.lidar.growing, v.lidar.correction) will be a point classification  in
       four categories:
       TERRAIN SINGLE PULSE (cat = 1, layer = 2)
       TERRAIN DOUBLE PULSE (cat = 2, layer = 2)
       OBJECT SINGLE PULSE (cat = 3, layer = 2)
       OBJECT DOUBLE PULSE (cat = 4, layer = 2)

EXAMPLES

   Basic correction procedure

       v.lidar.correction input=growing output=correction out_terrain=only_terrain

   Second correction procedure

       v.lidar.correction input=correction output=correction_bis out_terrain=only_terrain_bis

SEE ALSO

       v.lidar.edgedetection, v.lidar.growing, v.surf.bspline

AUTHORS

       Original version of program in GRASS 5.4:
       Maria Antonia Brovelli, Massimiliano Cannata, Ulisse Longoni and Mirko Reguzzoni
       Update for GRASS 6.X:
       Roberto Antolin and Gonzalo Moreno

REFERENCES

       Antolin,  R.  et  al.,  2006.  Digital  terrain  models  determination  by  LiDAR  technology:  Po  basin
       experimentation. Bolletino di Geodesia e Scienze Affini, anno LXV, n. 2, pp. 69-89.
       Brovelli M. A., Cannata M., Longoni U.M., 2004. LIDAR Data Filtering and DTM Interpolation Within  GRASS,
       Transactions in GIS, April 2004,  vol. 8, iss. 2, pp. 155-174(20), Blackwell Publishing Ltd.
       Brovelli M. A., Cannata M., 2004. Digital Terrain model reconstruction in urban areas from airborne laser
       scanning data: the method and an  example for Pavia (Northern Italy). Computers and Geosciences 30 (2004)
       pp.325-331
       Brovelli M. A. and Longoni U.M., 2003. Software per il filtraggio di dati LIDAR, Rivista dell?Agenzia del
       Territorio, n. 3-2003, pp. 11-22 (ISSN 1593-2192).
       Brovelli  M.  A.,  Cannata M. and Longoni U.M., 2002. DTM LIDAR in area urbana, Bollettino SIFET N.2, pp.
       7-26.
       Performances of the filter can be seen in the ISPRS WG III/3 Comparison of Filters report by Sithole,  G.
       and Vosselman, G., 2003.

       Last changed: $Date: 2010-09-16 00:25:59 -0700 (Thu, 16 Sep 2010) $

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       © 2003-2013 GRASS Development Team

GRASS 6.4.3                                                                           v.lidar.correction(1grass)